The present invention relates to an improved filter unit. More particular, the invention is directed to a plastic filter unit having a reservoir and a receptacle which are securely held together in the assembled state yet which may be readily assembled and disassembled.
Various types of sealing means have been used in the prior art in order to hold the receptacle and the reservoir together. One such method comprises the use of a tape along the outer periphery of the two pieces which after filtration of the liquid is pealed to allow disassembly. This method has numerous disadvantages in that the tape during transportation and storage tends to loosen to such a point that the assembly either comes apart or leaks air when a vacuum is applied to the filter unit.
Another method used to hold the assembly together is to provide mating treaded portions on the parts. However, during long periods of shelf retention the two parts are subject to loosening due to creep in the material. Threaded assembly's have a constant force which tends to unscrew the assembly. Therefore, during transit of the filter units vibration may cause loosening of parts, thereby resulting in the assembly either loosening or coming apart.
Applicant has invented an improved filter assembly which minimizes the disadvantages of the prior art. A filter assembly made in accordance with the present invention provides positive locking means to minimize or prevent loosening of the assembly during transit and storage.